In a long term evolution (LTE) wireless communication network, user equipment (UE), such as mobile phones or other wireless-enabled devices, intermittently exchange user data with an evolved Node B (eNodeB). The data may include voice over IP (VoIP), multimedia, Internet traffic, or other content and may be transmitted toward the network as uplink (UL) data or received from the network as downlink (DL) data.
From a management perspective, the UE is in one of three states: Detached, Idle, or Connected. When the UE is first turned on, it is in the detached state and does not have designated network resources available for data exchange. Upon registration with the network, the UE enters the connected state and has a radio resource control (RRC) connection with the eNodeB allowing data transfer. After an inactivity period where no user data is exchanged, the UE may enter an idle state to conserve network resources and UE battery life. The UE may re-enter the connected state from the idle state when new data transfer is imminent.
The maximum number of UEs that can be supported by an eNodeB is finite. When the limit is about to be reached, some UEs may be transitioned to the idle state via radio resource control (RRC) connection release to give room for new calls and incoming handover (HO) requests. UEs selected for RRC release can be those that are “dormant” and have not been using UL and DL bearer services for some time. Released UEs remain attached to the network and may trigger a new RRC connection request when bearer traffic starts.
Although non-revenue-generating, these transitions of Connected to Idle contribute to the signaling load to be processed by various network elements. Frequent transitions of UE states from Connected to Idle (RRC release and S1Release) and from Idle back to Connected (Service Requests) can significantly impact capacity and performance of the eNodeB and evolved packet core (EPC). In addition, once UEs are in the Idle state, network originated Service Requests require paging which will increase signaling traffic, increase usage of radio frequency (RF) resources, and lengthen delays for UEs configured with longer paging cycle (up to 2.5 seconds) to monitor the paging channel.
With the introduction of new applications and devices, it can be very difficult to predict the amount of signaling traffic load that each Network Element (eNodeB/EPC) needs to support. This presents a challenge for operators since deployment of new devices or applications can cause congestion and overload conditions in the network. This may require re-engineering of the network and deployment of additional nodes (which can take several months).